M. J. Vicente Vacas

Neutrino Energy Reconstruction and the Shape of the CCQE-like Total Cross Section

We show that because of the multinucleon mechanism effects, the algorithm used to reconstruct the neutrino energy is not adequate when dealing with quasielastic-like events, and a distortion of the total flux-unfolded cross-section shape is produced. This amounts to a redistribution of strength from high to low energies, which gives rise to a sizable excess (deficit) of low (high) energy neutrinos. This distortion of the shape leads to a good description of the MiniBooNE unfolded charged current quasielastic-like cross sections published by A. A. Aguilar-Arevalo et al. [(MiniBooNE Collaboration), Phys. Rev. D 81, 092005 (2010)]. However, these changes in the shape are artifacts of the unfolding process that ignores multinucleon mechanisms.

Production of pionic modes in relativistic heavy-ion collisions☆

Abstract Production of pionic modes in heavy-ion collisions of energy E /nucleon ≈1 GeV is substantially enhanced by interactions of the pions with the medium. These interactions provide a momentum-dependent index of refraction for the pions, making Cherenkov radiation of them possible for nucleons traversing such media. Schematic and realistic calculations of these processes are presented.

Protonium annihilation into two mesons

The available branching ratios for protonium annihilation into two mesons are analyzed in terms of a hadronic picture. We start from protonium wave functions calculated using a realistic OBE potential, a phenomenological part to account for the annihilation, and a particularly simple transition operatorV(N¯N → mesona + mesonb). Flavour effects, sensitivity to tensor mixing and to isospin mixing are investigated.

Octet-baryon axial-vector charges and SU(3)-breaking effects in the semileptonic hyperon decays

The octet-baryon axial-vector charges and the g1/f1 ratios measured in the semileptonic hyperon decays are studied up to O(p^3) using the covariant baryon chiral perturbation theory with explicit decuplet contributions. We clarify the role of different low-energy constants and find a good convergence for the chiral expansion of the axial-vector charges of the baryon octet, g1(0), with O(p^3) corrections typically around 20% of the leading ones. This is a consequence of strong cancellations between different next-to-leading order terms. We show that considering only non-analytic terms is not enough and that analytic terms appearing at the same chiral order play an important role in this description. The same effects still hold for the chiral extrapolation of the axial-vector charges and result in a rather mild quark-mass dependence. As a result, we report a determination of the leading order chiral couplings, D=0.623(61)(17) and F=0.441(47)(2), as obtained from a completely consistent chiral analysis up to O(p^3). Furthermore, we note that the appearance of an unknown low-energy constant precludes the extraction of the proton octet-charge from semileptonic decay data alone, which is relevant for an analysis of the composition of the proton spin.

Watson's theorem and the

We present a new determination of the

N\Delta(1232)

Nmathrm{ensuremath{Delta}}

axial transition

axial form factors from neutrino induced pion production data. For this purpose, the model of Hernandez et al. [Phys. Rev. D 76, 033005 (2007)] is improved by partially restoring unitarity. This is accomplished by imposing Watsons theorem on the dominant vector and axial multipoles. As a consequence, a larger

Two-meson doorway model of low energy antiproton-proton annihilation☆

{C}_{5}^{A}(0)

Nuclear medium effects in

, in good agreement with the prediction from the off-diagonal Goldberger-Treiman relation, is now obtained.

\nu(\bar\nu)

We investigate a semiclassical model for pp annihilation into any number of pions and kaons at antiproton lab momenta plab < 3 GeV/c, based on the hypothesis of two-meson doorway states as intermediate channels in the annihilation process. All relevant selection rules are incorporated. We find that with baryon radii of about 0.6 fm, the energy dependence of partial cross sections in all important annihilation channels can be reproduced successfully. Angular distributions for pp → π+π− and K+K− can also be described, provided one admits a substantial s-wave suppression in this model.